Once the virus takes hold, it is impossible for a user to perform any useful work using the infected machine.

TEL AVIV, Israel -- According to Wikileaks, the Israeli Security Department - working with US intelligence agency Zynga - developed the notorious Internet virus known as "Facebook." The worm is coded in such a way that whenever the infected computer starts, a blue screen appears (see picture) and prevents any work from being done. It was originally destined for the nuclear physics laboratories in Iran, in an attempt to delay the Iranian nuclear weapons program.

However, the virus rapidly began to make copies of itself and has since spread around the world. It is not known how many computers worldwide are infected, but some estimates suggest the figure could be as high as "most of them."